The present proposal is concerned chiefly with defining the contribution of the two intestinal lecithin synthetic pathways toward the lecithin associated with lipoproteins and specifically chylomicrons. These two pathways, a) lysolecithin acyltransferase and b) cholinephosphotransferse will be valuated in bile and intestinal lymphatic fistulated rats by a series of experiments using radiolabeled precursors of both pathways. The exchange of radiolabeled chylomicron lecithin for non-radiolabeled lecithin during the collection periods will be evaluated as will the contribution of blood lysolecithin to chylomicron lecithin.